Disulfide compound

ABSTRACT

A novel disulfide compound is presented which can be readily led to 5-amino-2-chloro-4-fluoro-thiophenol in good yield. 
     A bis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide compound represented by the formula (1): ##STR1##

TECHNICAL FIELD

The present invention providesbis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide which is useful asan intermediate material for a thiadiazabicyclononane-type agriculturalchemical such as a herbicide.

BACKGROUND ART

As a thiadiazabicyclononate-type agricultural chemical, a compound whichhas a structure of the following formula: ##STR2## and which is used asan active substance for a herbicide, is, for example, known (seeJapanese Unexamined Patent Publication No. 264489/1988). The compound ofthis formula (2) (hereinafter represented also as the compound (2), thesame applies to other compounds) is produced by using5-amino-2-chloro-4-fluoro-thiophenol represented by the formula (3) (seeU.S. Pat. No. 4,613,675) as the starting material: ##STR3##

Heretofore, as a method for obtaining the above compound (3), thefollowing method is known which is a combination of the methodsdisclosed in Japanese Unexamined Patent Publications No. 172958/1985 andNo. 33148/1987: ##STR4##

However, the above conventional method had problems with respect to thesafety and toxicity, etc. such that it was necessary to use fummingsulfuric acid containing 60% of SO₃ which was not easy to use forindustrial operation, and besides, phosgene was generated during thereaction using carbon tetrachloride as a solvent. Further, for thereduction of the chlorosulfonyl group, a large amount of a reducingagent as well as an excess amount of an acid was required to be used.Therefore, such a method was not satisfactory as an industrial method.

On the other hand, as a method for obtaining the above compound (3), thefollowing method is also known involving a disulfide compound as anintermediate (see Unexamined Patent Publication No. 221254/1990).##STR5##

However, in the above method, the diazotization operation is cumbersome.Besides, the yield is low, a side reaction proceeds mainly in thenitration, and the yield is also low. Thus, using the disulfide compoundas an intermediate does not provide good results, and this method cannot necessarily be regarded as a good method.

The present invention has been made for a purpose of overcoming theabove mentioned difficulties of the prior art and to provide a noveldisulfide compound which can readily be led to the5-amino-2-chloro-4-fluoro-thiophenol of the above formula (3) in goodyield.

DISCLOSURE OF THE INVENTION

In order to accomplish the above object, the present invention providesa bis-(5-acetoamino-2-chloro-4-fluorobenzene)disulfide compoundrepresented by the formula (1): ##STR6##

Now, with reference to the following reaction formula, thebis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide compound of thepresent invention represented by the formula (1) and a method forleading the disulfide compound (1) to the above mentioned5-amino-2-chloro-4-fluoro-thiophenol (3), will be described. ##STR7##

Namely, as the operation to obtainbis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide (1) as the disulfidecompound of the present invention, 4-chloro-2-fluoroacetanilide (4) andsulfur monochloride are reacted in the presence of a Lewis acid at atemperature of from 0° to 100° C., preferably from 20° to 50° C.

The Lewis acid to be used in the above operation, may, for example, bealuminum chloride, iron chloride or zinc chloride. Among them, aluminumchloride is preferably used to attain a good yield.

Further, as a solvent, it is possible to use a solvent inert to thereaction to smoothly conduct the reaction. As such a solvent, an organicsolvent such as a halogenated hydrocarbon, may, for example, bepreferred, and dichloromethane, chloroform or dichloroethane may beused.

The amount of sulfur monochloride to be used in the above operation, is0.5 mol or more, preferably from 0.6 to 2.5 mols, per mol of thecompound (4). Further, the amount of the Lewis acid is from 1 to 5 mols,preferably from 2 to 2.5 mols, per mol of the compound (4). On the otherhand, when an organic solvent is used, it may be at least an amountwhere stirring can be conducted.

Further, the 4-chloro-2-fluoroacetanilide (4) to be used as the startingmaterial can easily be obtained by a method of acylating an aniline asdisclosed in Japanese Unexamined Patent Publication No. 51521/1976.

The disulfide compound (1) of the present invention thus obtained can beled to 5-amino-2-chloro-4-fluoro-thiophenol (3) by reducing it with zincmetal in acetic acid, followed by hydrolysis with an aqueous alkalinesolution.

Further, the above 5-amino-2-chloro-4-fluoro-thiophenol (3) can be ledto an active compound of a thiadiazabicyclononane-type herbicidedisclosed in Japanese Unexamined Patent Publication No. 264489/1988, asshown below: ##STR8##

The present invention provides novelbis-(5-acetamino-2-chloro-4-fluorobezene)disulfide (1) by reacting4-chloro-2-fluoroacetanilide (4) and sulfur monochloride in the presenceof a Lewis acid. Further, as shown in the following Reference Example,the disulfide compound (1) of the present invention can be converted to5-amino-2-chloro-4-fluoro-thiophenol (3) by reduction and hydrolysis.

Accordingly, the present invention can be an intermediate useful for athiadiazabicyclononane-type compound having herbicidal activities asdisclosed in Japanese Unexamined Patent Publication No. 264489/1988.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described specifically with referenceto Examples and Reference Examples.

EXAMPLE 1 Preparation ofbis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide

In a 100 ml reaction flask equipped with a condenser, a thermometer anda stirrer, 7.5 g (0.04 mol) of 4-chloro-2-fluoro-acetanilide wassuspended in 40 cc of dichloromethane, and 10.7 g (0.08 mol) ofanhydrous aluminum chloride was added thereto. The mixture was stirredat room temperature for 30 minutes, and then 4.1 g (0.03 mol) of sulfurmonochloride was dropwise added thereto from a dropping funnel. Aftercompletion of the dropwise addition, the mixture was reacted at 40° C.for 3 hours. Then, the reaction solution was cooled to room temperatureand poured into 200 g of ice water. The organic layer was extracted with150 ml of ethyl acetate and dried. Then, dichloromethane and ethylacetate as the solvents were distilled off under reduced pressure, andthe residue was washed with a small amount of ethyl acetate to obtain7.4 g of bis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide (1). Yieldwas 84.7%. The physical properties and confirmation data are shownbelow.

Physical property: melting point of 241°-3° C.

Confirmation data

1H-NMR[SO(CD₃)]: 9.8(2H,s), 7.39-8.49(4H,q), 2.10(6H,s) MS: Peaksattributable to chlorine isotope were found at P+2 and P+4 based on436(P).

EXAMPLE 2 Preparation ofbis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide

In a 100 ml reaction flask equipped with a condenser, a thermometer anda stirrer, 7.5 g (0.04 mol) of 4-chloro-2-fluoro-acetanilide wassuspended in 40 cc of dichloromethane, and 10.7 g (0.08 mol) ofanhydrous aluminum chloride was added thereto. The mixture was stirredat room temperature for 30 minutes, and then 8.1 g (0.06 mol) of sulfurmonochloride was dropwise added thereto by a dropping funnel. After thecompletion of the dropwise addition, the mixture was reacted at 40° C.for 3 hours. Then, the reaction solution was cooled to room temperatureand poured into 200 g of ice water. The organic layer was extracted with150 ml ethyl acetate and dried. Then, dichloromethane and ethyl acetateas the solvents were distilled off under reduced pressure, and theresidue was washed with a small amount of ethyl acetate to obtain 6.9 gof bis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide (1). Yield was79.3%.

REFERENCE EXAMPLE 1 Preparation of5-acetamino-2-chloro-4-fluorothiophenol

In a 200 ml reaction flask, 6.4 g (0.0146 mol) ofbis-(5-acetamino-2-chloro-4-fluorobenzene)disulfide and 9.8 g (0.149mol) of zinc were suspended in 100 cc of acetic acid and reacted for 6hours under reflux. After cooling to room temperature, inorganicsubstances were filtered, and acetic acid was distilled off underreduced pressure, whereby 4.8 g of5-acetamino-2-chloro-4-fluoro-thiophenol was obtained as white crystalshaving a melting point of 142.5°-144° C. Yield was 73.1%.

REFERENCE EXAMPLE 2 Preparation of 5-amino-2-chloro-4-fluoro-thiophenol

Into a 100 ml reaction flask, 4.8 g (0.022 mol) of5-acetamino-2-chloro-4-fluoro-thiophenol, 2.55 g (0.064 mol) of sodiumhydroxide and 25.5 cc of water were added and stirred under reflux for 4hours to obtain a uniform solution. The solution was cooled to roomtemperature and neutralized with 10% hydrochloric acid. The precipitatedsolid was extracted with 25 cc of ethyl acetate, followed by removal ofwater and distillation under reduced pressure to obtain 3.8 g of5-amino-2-chloro-4-fluoro-thiophenol as slightly yellow crystals.

Yield was 97.9%.

Physical property: melting point of 64.5°-66.0° C.

Confirmation data: H-NMR(CDCl₃) 3.42(2H,s), 3.70(1H,s), 6.68(1H,d,J=8Hz), 6.97(1H,d,J=10 Hz)

We claim:
 1. A bis-(5-acetoamino-2-chloro-4-fluorobenzene)disulfidecompound represented by the formula (1): ##STR9##